I'm new to this forum and have a quick question. I'm sure someone here can answer it. I apologize for the ignorance, I'm relatively new to the subject.

First of all, I understand that evolution does not need the fossil record to prove anything, this is mainly a curiosity.

So I do not really understand the "Fossil rabbits in the Precambrian!" argument. I understand it at a base level: Mammals cannot exist before the first mammal. Or basically animals cannot exist before the first animal. Easy. (Ignore the awful usage of animal when talking about Cambrian/Precambrian) But it also seems circular. It seems like one needs to assume evolution is true in order to make this claim. However, I see this claim used often as a potential way to disprove evolution.

Throw out the rabbit, that seems silly. The root argument seems to be, a fossil can't exist before it's era. Can't find a fossil out of order. My question is, why not? If you use the extreme example of *insert animal* in the Precambrian, this makes sense. Otherwise, I don't quite get it.

For example, we have found animals living in eras far before the time we believed them to live. Biologists simply shift back the time on the evolutionary clock, saying that they must have evolved before the time we previously thought. If we found a living animal with fossils earlier than originally predicted, would we call them living fossils, and be done with it? Then use evolution to explain?

A creationist would say "Hey, this *insert animal* was here the whole time! As was everything else!"

An evolutionist would (maybe?) say "This *insert animal* was here the whole time, but all *insert animal* species we know today share that *insert animal* as a common ancestor. The ancestor of that *insert animal* is different because it lived in an era/region where potential improvements existed, and natural selection helped it along toward obtaining those improvements. This wasn't necessarily true everywhere. *insert animal* also lived in era/region, and there it happened to need no improvements, so natural selection took a vacation."

I don't understand why there couldn't be two simultaneous chains of evolution, independent of each other, in different parts of the world, with one happening to converge faster to what we know of as a rabbit, and therefore rabbit fossils in that region would appear earlier.

So, tell me where I'm wrong.

TL;DR version: How can finding a fossil in the wrong era be so 'detrimental' to the theory of evolution?